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GPX 250 - Is there a problem with my brakes?

Discussion in 'Technical and Troubleshooting Torque' at netrider.net.au started by Nocker, Jun 28, 2007.

  1. Hi All,

    On the weekend I changed the engine oil again and the brakes (front and rear) for the first time.

    The rear seems to be fine as a result.

    The front however... I think has a problem. It feels like the pads are gripping the disk all the time. There feels like there is too much friction. E.g. when I'm riding along and when I let off the throttle there seems to be a lot of strain on the front, much more than before.

    If it helps any here is basically the process that I did to change the pads:
    - Unbolt the caliper
    - Push the slide back to remove the pads
    - Press the pistons back as far as possible
    - Place the new pads in the caliper
    - Move the slide back over the pads
    - Put the caliper back over the disk
    - Bolt the caliper back on
    - Squeezed the brake lever until pressure was built up



    I was just wondering if there was a spring or something that I missed that is meant to retract the pistons just that little bit so that the pads aren't gripping the disk too much?

    Any help is appreciated.

    Here is the image if that helps. I don't know what the arrow is pointing at.
    exploded_caliper.
     
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  2. get the wheel off the ground. It should spin in your hand.

    If the new pads are thicker it could be the reservoir is now under pressure if you didn't crack the lid when you put the new pads in.

    If that's not the case you may be up for rebuild kits for either your master cylinder and/or you calipers.
     
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  3. Agree with him^

    You probably have some residual pressure in the lines. For fun, crack open a bleed screw a half turn and see what happens. Hopefully you haven't cocked a piston.

    Regards, Andrew.
     
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  4. Thanks guys,

    I thought that it may be some sort of pressure in the lines. Like maybe someone topped up the brake fluid when the old pads were low on thickness.

    I even thought that there may have been some sort of adjustment at the lever or something.

    The wheel definitely wouldn't spin in my hand if I tried.

    Typhoon, when you say "cocked" the piston what do you mean? Did you miss type and mean cooked (as in too hot)? Or do you mean I could have stuffed/broken the piston somehow because there is too much pressure?

    I definitely didn't crack the reservoir lid while putting in the new pads. So I'll try opening the bleed screw and a bit and then closing it up again.

    Thanks for the advice guys.
     
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  5. Oh, but also does it still sound like there is too much pressure in the lines when I had to pump up the brake lever?
     
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  6. I meant cocked. As in, the piston cocks over in it's bore if incorrectly pushed back.
    If the reservoir is pressurised (as in too much fluid) you will still be able to move the lever. Cracking a bleed screw will relieve any if this pressure, and won't harm anything if you do it briefly.

    Regards, Andrew.
     
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  7. Thanks,

    I have now cracked the bleed screw and a little bit of brake fluid came out.

    The brakes feel better now and I think that it is all OK. When I spin the wheel it spins more freely however the pads do still have contact with the rotor.

    Thanks for all the advice.
     
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